For over fifty (50) years automotive engine oils have been formulated with zinc dialkyl dithio phosphate (ZDDP) resulting in low levels of wear, oxidation, and corrosion. The additive is truly ubiquitous and found in nearly every modern engine oil. ZDDP may impart multifunctional performance in the areas of anti-wear, anti-oxidation, and anti-corrosion and is considered one of the most cost-effective additives in general use by engine oil manufacturers and marketers.
However, not all ZDDP's are effective for improving lubricant performance without the formation of unwanted piston deposits. In general, there are three primary classes of ZDDP's in common use in engine oils, ZDDP's made with primary alcohols, ZDDP's made with secondary alcohols, and ZDDP's made with a mixture of primary and secondary alcohols. Also, mixtures of all primary alcohol ZDDP with all secondary alcohol ZDDP have been used. In addition to the alkoxy moiety derived from primary or secondary alcohols, the alcohol chain length may also have an effect on lubricant performance. Accordingly, there may be an unlimited number of combinations of primary and secondary alcohol ZDDP's with varying chain lengths that are potentially useful for engine lubricant applications. Some combinations of ZDDP's may increase piston deposit formation and some combinations of ZDDP's may decrease engine deposit formation. Accordingly, what is needed is a ZDDP product composition that provides enhances lubricant performance and does not increase piston deposit formation.
In view of the above, an embodiment of the disclosure provides a lubricant composition for reducing engine deposits. The lubricant composition includes a base oil having a NOACK volatility of from about 5 to about 15 and a zinc dialkyl dithio phosphate composition. The zinc dialkyl dithio phosphate composition has at least about 65 mole percent of zinc dialkyl dithio phosphate compounds derived from all primary alcohols, wherein the zinc dialkyl dithio phosphate composition has greater than about 40 mole percent zinc dialkyl dithio phosphate compounds having alkoxy moieties derived from alcohols having four carbon atoms.
In another embodiment a lubricant composition may include a base oil having a NOACK volatility of from about 5 to about 15 and a zinc dialkyl dithio phosphate composition having from about 15 to about 30 mole percent of zinc dialkyl dithio phosphate compounds derived from alcohols having five carbon atoms.
Yet another embodiment of the disclosure may provide a method for decreasing piston deposits in an internal combustion engine. The method includes lubricating the engine with a lubricant composition having therein a base oil having a NOACK volatility of from about 5 to about 15, and a zinc dialkyl dithio phosphate composition. The zinc dialkyl dithio phosphate composition has at least about 65 mole percent of zinc dialkyl dithio phosphate compounds derived from all primary alcohols, wherein the zinc dialkyl dithio phosphate composition has greater than about 40 mole percent zinc dialkyl dithio phosphate compounds having alkoxy moieties derived from alcohols having four carbon atoms.
Another embodiment of the disclosure provides a method for engine deposits in an internal combustion engine. The method includes lubricating the engine with a lubricant composition having therein a base oil having a NOACK volatility of from about 5 to about 15 and a zinc dialkyl dithio phosphate composition having from about 15 to about 30 mole percent of zinc dialkyl dithio phosphate compounds derived from alcohols having five carbon atoms.
The compositions and methods described may be particularly suitable for improving engine deposit ratings over combinations of ZDDP compounds that do not contain a sufficient amount of ZDDP compounds made with primary alcohols or that have a lower mole percentage of alkoxy moieties derived from alcohols having more than 5 carbon atoms. Other features and advantages of the compositions and methods described herein may be evident by reference to the following detailed description which is intended to exemplify aspects of the embodiments without intending to limit the embodiments described herein.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the embodiments disclosed and claimed.